In machinery operations requiring precise positioning and clamping of a workpiece in a rotating chuck, it has been conventional to clamp the workpiece in a plurality of tool holders disposed on the chuck so that the tool holders are symmetrically arranged about a rotational axis of the chuck. Precision tool holders generally comprise a master jaw adjustably disposed on the chuck and often forming a part of the chuck as in the case of master jaws welded to a diaphragm of a diaphragm chuck, and in the case of a master jaw which forms an integral part of an adjustable rock arm in a Bal-Lok.RTM. chuck. The foregoing types of chucks generally provide for a limited range of precise adjustability and therefore require that the workpiece be clamped in a top jaw that may be interchangeably connected to the master jaw in order to accommodate different size workpieces. Interchangeable top jaws however, often require complete disassembly of the tool holder, which is laborious, time consuming, and often results in misplaced parts. To overcome these problems, it has been suggested to interconnect a top jaw to a master jaw with a key locator having a wedge-shaped foot and a lock bolt which may be loosened to disconnect the wedge-shaped foot of the key locator to the master jaw without removing the key locator or the lock bolt from the master jaw. In this manner, different top jaws may be interchangeably connected to the master jaw. Interchangeable tool holder assemblies however are subject to forces from the workpiece which cause reaction forces in the jaw assembly that adversely effect the precise positioning and clamping of the workpiece on the chuck. For example, in interchangeable jaw assemblies of the type discussed above, forces exerted by the workpiece on the top jaw cause, among other reactions, tensile stresses in the key locator which interconnects the top jaw to the master jaw. These tensile stresses result in stretching of the key locator which permits the top jaw to separate from the master jaw, shown exaggerated in FIG. 5, resulting in imprecise alignment and clamping of the workpiece. Accordingly, there is a demonstrated need for an advancement in the art of interchangeable tool holders.
It is therefore an object of the present invention to provide a novel locking jaw assembly for precisely clamping and positioning a workpiece.
It is also an object of the present invention to provide a novel locking jaw assembly that is economical to use and manufacture.
It is a further object of the present invention to provide a novel locking jaw assembly having a workpiece clamping top jaw securely interconnectable to a master jaw by a key locator and a lock bolt.
It is another object of the present invention to provide a novel locking jaw assembly wherein the secure interconnection of the top jaw to the master jaw by the key locator and the lock bolt is augmented by a master jaw lip received in a complementary groove on the top jaw.
It is yet another object of the present invention to provide a novel locking jaw assembly having a top jaw that may be readily and precisely replaced with another top jaw without completely disassembling the locking jaw assembly.
Accordingly, the present invention is directed toward a novel locking jaw assembly having a workpiece clamping top jaw securely interconnectable to a master jaw by a key locator and a lock bolt, wherein the top jaw may be readily removed from the master jaw by simply loosening the lock bolt, and another top jaw may be readily interconnected to the master jaw with repeatable precision by re-tightening the loosened lock bolt. The key locator includes a T-shaped body portion that is received and retained in a T-shaped slot of the master jaw by the lock bolt. A wedge-shaped foot having a T-shaped cross section extending from the key locator body portion is disposable in a wedge-shaped recess of the top jaw, and, upon rotation of the lock bolt, may be slidably moved into a wedge-shaped slot at an outer end of the top jaw, thereby fastening the top jaw to the master jaw. The interconnection of the top jaw to the master jaw by the key locator and lock bolt is augmented by a lip portion of the master jaw received in a complementary shaped groove disposed in a flange at an inner end of the top jaw wherein forces exerted by the workpiece on the top jaw tend to move the top jaw into closer contact with the master jaw and relieve tensile stresses on the key locator. These and other objects, features and advantages of the present invention will become apparent upon consideration of the following Detailed Description of the Invention with the accompanying drawings.